Computer networks generally implement one or more network protocols. Some computer networks implement legacy cell-based network protocols, such as an Asynchronous Transfer Mode (ATM) network protocol. More recently, computer networks have been migrating to packet-based network protocols, such as an Internet Protocol (IP), where packets are switched through the computer network via various network segments referred to as “next hops.” While the packet-switched computer networks provide many benefits in terms of cost and data routing, various network services often require connections that resemble those of legacy computer networks.
To emulate these connections, packet-switched computer networks support a service commonly referred to as a “pseudowire.” Pseudowires (PWs) are defined paths with packet-switched networks that emulated physical connections. That is, one established within the network, a PW provides a multi-hop path for forwarding traffic between a source device and at least one destination device as if the devices were connected by a direct, physical connection. Commonly, the source devices are referred to as ingress devices of the PW and the destination devices are referred to as egress devices. Usually, the ingress and egress devices reside within the same computer network and are usually located at the edges of the computer network. That is, a PW typically emulates a single physical connection that spans the computer network. When the computer network comprises a single autonomous system (AS) or interior gateway protocol (IGP) domains, this form of PW is often referred to as single-segment (SS) PWs (SS-PWs) in that this form of PW is commonly set up directly between two provider edge (PE) devices of the AS or IGP domains. When the computer network includes two or more ASes or IGPs and the PW spans two or more of the domains, e.g., ASes, this form of PW is often referred to as a cross-domain PW. Traditionally PWs were limited to a single AS, but recent advances in PWs have enabled these single AS PWs to be linked or stitched together to form a type of cross-domain PW referred to as a multi-segment PW (MS-PW). In contrast to SS-PWs, a multi-segment PW refers to a statically or dynamically configured set of two or more contiguous PW segments that each behave and function as a single point-to-point PW. The term “PW segment” refers to a single segment or a part of a multi-segment PW, which is set up between two PE devices. More information regarding PWs and the architecture required to support PWs is available in Request for Comments (RFC) 3985, entitled “Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture,” dated March 2005, the entire contents of which are hereby incorporated by references as if set forth in its entirety herein. More information regarding the requirements for MS-PW is available in RFC 5254, entitled “Requirements for Multi-Segment Pseudowire Emulation Edge-to-Edge (PWE3),” dated October 2008, the entire contents of which are hereby incorporated as if fully set forth in its entirety herein.
As one example, service provider networks organized as separate ASes and may utilize a MS-PW to transport traffic across the ASes. In this scenario, provider edge (PE) routers located at the edge of the ASes form the MS-PW to transport layer 2 (L2) traffic between customer networks, where the L2 traffic typically takes the form of Ethernet frames or ATM cells. This traffic may be encapsulated and tunneled through the packet-switched service provider networks along the MS-PW. To form the MS-PW, the PE devices may be statically configured to support the MS-PW. However, the static configuration of pseudowires is burdensome to administrators of the service provider networks.
Alternatively, the MS-PW may be dynamically configured. In the dynamic configuration of MS-PW, the ingress and egress PE devices are required to support a specific layer three (L3) routing protocol referred to as a Border Gateway Protocol (BGP) that includes extensions for communicating MS-PW information. The PE devices establish BGP peering session with each other and exchange the MS-PW information across the ASes. The requirement to deploy this specific network routing protocol on all PE devices that operate as ingresses or egresses of MS-PWs may be restrictive and burdensome on the service provider. For example, the PE devices may not otherwise be configured to communicate across the ASes directly and, may not otherwise even be configured to implement BGP. BGP is a complex routing protocol typically used to communicate routing information between border routers of different service provider networks.